Bone morphogenetic proteins (BMPs) and growth/differentiation factors (GDFs) are part of a family of proteins which have been identified as having the ability to induce the growth, formation, differentiation and maintenance of various tissues, including bone, cartilage, tendon/ligament, muscle, neural, and various organs. BMPs and GDFs are subfamilies within the TGF-.beta. superfamily.
The TGF-.beta. superfamily of proteins have been shown to bind to serine/threonine kinase receptors. Massague, Cell 69:1067-1070 (1992); Attisano et al., Cell 68:97-108 (1992); Lin et al., Cell 68:775-785 (1992); Wang, et al., Cell 67:797-805 (1991). Similarly, activin receptors have been isolated and characterized as a predicted transmembrane serine kinase. Mathews et al., Cell 65:973-982 (1991); Nakamura et al., J. Biol. Chem. 267:18924-18928 (1992). Ebner et al., Science, 260:1344-1348 (1993) describe the existence of Type I and Type II TGF-.beta. receptors, and the effects of the Type I receptor on binding of TGF-.beta. to the Type II receptor.
Follistatin is a protein which has been identified as a molecule which is able to bind to activin, another member of the TGF-.beta. superfamily, and as a possible antagonist of activin. U.S. Pat. No. 5,545,616. Accordingly, follistatin has been suggested for possible use to predict and/or prevent preterm labor and to suppress FSH secretion from the pituitary [U.S. Pat. No. 5,545,616]; to have inhibin like activity [U.S. Pat. No. 5,041,538]; and for use in rheumatoid arthritis [AU9675056, Kaneka Corp].